//go:build ignore

//kage:unit pixels

package main

var Time float

func hash21(p vec2) float {
	p = fract(p * vec2(123.34, 456.21))
	p += dot(p, p + 45.32)
	return fract(p.x * p.y)
}

func smoothNoise(p vec2) float {
	ip := floor(p)
	fp := fract(p)
	fp = fp * fp * (3.0 - 2.0 * fp)
	ul := hash21(ip + vec2(0.0, 0.0))
	ur := hash21(ip + vec2(1.0, 0.0))
	ll := hash21(ip + vec2(0.0, 1.0))
	lr := hash21(ip + vec2(1.0, 1.0))
	a := mix(ul, ur, fp.x)
	b := mix(ll, lr, fp.x)
	return mix(a, b, fp.y)
}

func Fragment(dstPos vec4, srcPos vec2, color vec4) vec4 {
	original := imageSrc3UnsafeAt(srcPos)
	sp := srcPos * 15.0
	t := Time * 2.0
	n := smoothNoise(sp + t)
	sparkle := pow(n, 4.0) * 2.0
	sparkle = min(sparkle, 1.0)
	sparkleColor := mix(original, vec4(1.0, 0.9, 0.5, 1.0), sparkle)
	output := mix(original, sparkleColor, original.a)
	return output
}